void main(void)
{
    SeqStack S;
    char x, y;
    StackInitiate(&S);
    x = 'a'; y = 'b';
    StackPush(&S, y); StackPush(&S, 'c'); StackPush(&S, x);
    StackPop(&S, &y); StackPush(&S, 'd'); StackPop(&S, &x);
    StackPush(&S, 's');
    while(StackNotEmpty(S))
    {
        StackPop(&S, &y);
        printf("%c ", y);
    }
    printf("%c ", x);
}
